Process for generation of polyols from saccharides

ABSTRACT

A process for generating at least one polyol from a feedstock comprising saccharide is performed in a continuous or batch manner. The process involves, contacting, hydrogen, water, and a feedstock comprising saccharide, with a catalyst system to generate an effluent stream comprising at least one polyol and recovering the polyol from the effluent stream. The catalyst system comprises at least one unsupported component and at least one supported component.

FIELD OF THE INVENTION

The invention relates to process for generating at least one polyol froma saccharide containing feedstock using a catalyst system. The processinvolves, contacting hydrogen, water, and a feedstock comprisingsaccharide, with a catalyst system to generate an effluent comprising atleast one polyol and recovering the polyol from the effluent. Thecatalyst system comprises both an unsupported catalytic component and asupported catalytic component.

BACKGROUND OF THE INVENTION

Polyols are valuable materials that find use in the manufacture of coldweather fluids, cosmetics, polyesters and many other synthetic products.Generating polyols from saccharides instead of fossil fuel-derivedolefins can be a more environmentally friendly and a more economicallyattractive process. Previously, polyols have been generated frompolyhydroxy compounds, see WO 2006/092085 and U.S. 2004/0175806.Recently, catalytic conversion of saccharide into ethylene glycol oversupported carbide catalysts was disclosed in Catalysis Today, 147,(2009) 77-85. U.S. 2010/0256424, U.S. 2010/0255983, and WO 2010/060345teach a method of preparing ethylene glycol from saccharide and atungsten carbide catalyst to catalyze the reaction. Tungsten carbidecatalysts have also been published as successful for batch-mode directcatalytic conversion of saccharide to ethylene glycol in Angew. Chem.Int. Ed 2008, 47, 8510-8513 and supporting information. A small amountof nickel was added to a tungsten carbide catalyst in Chem. Comm. 2010,46, 862-864. Bimetallic catalysts have been disclosed in ChemSusChem,2010, 3, 63-66. Additional references disclosing catalysts known in theart for the direct conversion of cellulose to ethylene glycol orpropylene glycol include WO2010/060345; U.S. Pat. No. 7,767,867; Chem.Commun., 2010, 46, 6935-6937; Chin. J. Catal., 2006, 27(10): 899-903;and Apcseet UPC 2009 7^(th) Asia Pacific Congress on Sustainable Energyand Environmental Technologies, “One-pot Conversion of JerusalemArtichoke Tubers into Polyols.

However, there remains a need for new catalyst systems effective fordirect conversion of saccharide to polyol, and especially for catalystsystems that may be better suited for larger scale production or ongoingproduction. The catalyst system comprising at least one unsupportedcomponent and at least one supported component for generating at leastone polyol from a saccharide containing feedstock described hereinaddresses this need.

SUMMARY OF THE INVENTION

The invention employs a catalyst system useful for the conversion of atleast one saccharide to polyol, the catalyst system comprising anunsupported component comprising a compound selected from the groupconsisting of a tungsten compound, a molybdenum compound, and anycombination thereof, and a supported component comprising an activemetal component selected from the group consisting of Pt, Pd, Ru, Rh,Ni, Ir, and combinations thereof on a solid catalyst support. The solidcatalyst support is selected from the group consisting of carbon, Al2O3,ZrO2, SiO2, MgO, CexZrOy, TiO2, SiC, silica alumina, zeolites, clays andcombinations thereof. The mass ratio of the unsupported component to thesupported component ranges from about 1:100 to about 100:1 on anelemental basis wherein the supported component comprises from about0.05 to about 30 mass percent, on an elemental basis, activated metal.The unsupported component of the catalyst system may be selected fromthe group consisting of tungstic acid, molybedic acid, ammoniummetatungstate, heteropoly compounds of tungsten, heteropoly compounds ofmolybdenum, heteropoly compounds of tungstic acid, heteropoly compoundsof molybedic acid, and combinations thereof. Measurements of theunsupported component and the supported component such as mass ratios,weight ratios, and mass percents are provided herein on an elementalbasis with respect to the tungsten, molybdenum, platinum, palladium,rhenium, ruthenium, nickel, and iridium.

One embodiment of the invention is a process for generating at least onepolyol from a feedstock comprising saccharide where the processcomprises contacting, hydrogen, water, and a feedstock comprising atleast one saccharide, with a catalyst system comprising an unsupportedcomponent comprising a compound selected from the group consisting of atungsten compound, a molybdenum compound, and any combination thereof,and a supported component comprising a supported active metal componentselected from the group consisting of Pt, Pd, Ru, Rh, Ni, Ir, andcombinations thereof on a sold catalyst support, to generate an effluentcomprising at least one polyol, and recovering the polyol from theeffluent. The process may be operated in a batch mode operation or in acontinuous mode operation.

Another embodiment of the invention is a continuous process forgenerating at least one polyol from a feedstock comprising at least onesaccharide. The process involves, contacting, in a continuous manner,hydrogen, water, and a feedstock comprising at least one saccharide,with a catalyst system to generate an effluent stream comprising atleast one polyol and recovering the polyol from the effluent stream. Thehydrogen, water, and feedstock, are flowed in a continuous manner. Theeffluent stream is flowed in a continuous manner. The process is acatalytic process employing a catalyst system comprising an unsupportedcomponent comprising a compound selected from the group consisting of atungsten compound, a molybdenum compound, and any combination thereof,and a supported component comprising a supported active metal componentselected from the group consisting of Pt, Pd, Ru, Rh, Ni, Ir, andcombinations thereof on a solid catalyst support.

In one embodiment, the contacting occurs in a reaction zone having atleast a first input stream and a second input stream, the first inputstream comprising at least the feedstock comprising at least onesaccharide and the second input stream comprising hydrogen. The firstinput stream may be pressurized prior to the reaction zone and thesecond input stream may be pressurized and heated prior to the reactionzone. The first input stream may pressurized and heated to a temperaturebelow the thermal decomposition temperature of the saccharide prior tothe reaction zone and the second input stream may be pressurized andheated prior to the reaction zone. The first input stream and the secondinput stream further comprise water.

In another embodiment of the invention, the polyol produced is at leastethylene glycol or propylene glycol. Co-products such as alcohols,organic acids, aldehydes, monosaccharides, disaccharides,oligosaccharides, polysaccharides, phenolic compounds, hydrocarbons,glycerol, depolymerized lignin, and proteins may also be generated. Inone embodiment, the feedstock may be treated prior to contacting withthe catalyst by a technique such as sizing, drying, grinding, hot watertreatment, steam treatment, hydrolysis, pyrolysis, thermal treatment,chemical treatment, biological treatment, catalytic treatment, orcombinations thereof.

The feedstock may be continuously contacted with at least the supportedcomponent of the catalyst system in a reactor system such as anebullating catalyst bed reactor system, an immobilized catalyst reactorsystem having catalyst channels, an augured reactor system, and a slurryreactor system. Examples of operating conditions include temperaturesranging from about 100° C. to about 350° C. and hydrogen pressuresgreater than about 150 psig. In one embodiment, the temperature in thereactor system may range from about 150° C. to about 350° C., in anotherembodiment the temperature in the reactor system may range from about200° C. to about 280° C. The feedstock may be continuously contactedwith the catalyst system in the reactor system operated, for example, ata water to feedstock comprising saccharide weight ratio ranging fromabout 1 to about 100, a catalyst system (unsupported component plussupported component) to feedstock comprising saccharide weight ratio ofgreater than about 0.005 with the catalyst system measured on anelemental basis, a pH of less than about 10 and a residence time ofgreater than five minutes. In another embodiment, the catalyst system tofeedstock comprising saccharide weight ratio is greater than about 0.01with the catalyst system measured on an elemental basis. The hydrogen,water, and feedstock may be contacted with the catalyst in a reactionzone operated at conditions sufficient to maintain at least a portion ofthe water in the liquid phase.

The effluent stream from the reactor system may further comprise thecatalyst system, which may be separated from the effluent stream using atechnique such as direct filtration, settling followed by filtration,hydrocyclone, fractionation, centrifugation, the use of flocculants,precipitation, liquid extraction, adsorption, evaporation, andcombinations thereof. Depending upon the application, the supportedcatalyst component, the unsupported catalyst component, or both may beseparated from the effluent stream.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a basic diagram of the flow scheme of one embodiment of theinvention. Equipment and processing steps not required to understand theinvention are not depicted.

FIG. 2 is a basic diagram of the flow scheme of another embodiment ofthe invention showing an optional pretreatment zone and an optionalsupported catalyst component separation zone with optional supportedcatalyst component recycle. Equipment and processing steps not requiredto understand the invention are not depicted.

DETAILED DESCRIPTION OF THE INVENTION

The invention involves a catalyst system and a process for generating atleast one polyol from a feedstock comprising at least one saccharide.The catalyst system comprises an unsupported component comprising acompound selected from the group consisting of a tungsten compound, amolybdenum compound, and any combination thereof, and a supportedcomponent comprising an active metal component selected from the groupconsisting of Pt, Pd, Ru, Rh, Ni, Ir, and combinations thereof on asolid catalyst support. Examples of suitable solid catalyst supportsinclude carbon, Al₂O₃, ZrO₂, SiO₂, MgO, Ce_(x)ZrO_(y), TiO₂, SiC, silicaalumina, zeolites, clays and combinations thereof. The process involvescontacting, hydrogen, water, and a feedstock comprising at least onesaccharide, with the catalyst system comprising an unsupported componentcomprising a compound selected from the group consisting of a tungstencompound, a molybdenum compound, and any combination thereof, and asupported component comprising a supported active metal componentselected from the group consisting of Pt, Pd, Ru, Rh, Ni, Ir, andcombinations thereof on a solid catalyst support, to generate aneffluent comprising at least one polyol, and recovering the polyol fromthe effluent. The process may be operated in a batch mode operation orin a continuous mode operation. When operated in a continuous mode, theprocess involves continuous catalytic conversion of a flowing stream offeedstock comprising saccharide to ethylene glycol or propylene glycolwith high yield and high selectivity.

The feedstock comprises at least one saccharide which may be any classof monosachharides, disaccharides, oligosachharides, and polysachharidesand may be edible, inedible, amorphous or crystalline in nature. In oneembodiment, the feedstock comprises polysaccharides that consist of oneor a number of monosaccharides joined by glycosidic bonds. Examples ofpolysaccharides include glycogen, cellulose, hemicellulose, starch,chitin and combinations thereof. The term “saccharide” as used herein ismeant to include all the above described classes of saccharidesincluding polysaccharides.

When the saccharide is cellulose, hemicellulose, or a combinationthereof, additional advantages may be realized. Economic conversion ofcellulose and hemicellulose to useful products can be a sustainableprocess that reduces fossil energy consumption and does not directlycompete with the human food supply. Cellulose and hemicellulose arelarge renewable resources having a variety of attractive sources, suchas residue from agricultural production or waste from forestry or forestproducts. Since cellulose and hemicellulose cannot be digested byhumans, using cellulose and or hemicellulose as a feedstock does nottake from our food supply. Furthermore, cellulose and hemicellulose canbe a low cost waste type feedstock material which is converted herein tohigh value products like polyols such as ethylene glycol and propyleneglycol.

The feedstock comprising saccharide of the process may be derived fromsources such as agricultural crops, forest biomass, waste material,recycled material. Examples include short rotation forestry, industrialwood waste, forest residue, agricultural residue, energy crops,industrial wastewater, municipal wastewater, paper, cardboard, fabrics,pulp derived from biomass, corn starch, sugarcane, grain, sugar beet,glycogen and other molecules comprising the molecular unit structure ofC_(m)(H₂O)_(n), and combinations thereof. Multiple materials may be usedas co-feedstocks. With respect to biomass, the feedstock may be wholebiomass including cellulose, lignin and hemicellulose or treated biomasswhere the polysaccharide is at least partially depolymerized, or wherethe lignin, hemicellullose or both have been at least partially removedfrom the whole biomass.

The process of the invention maybe operated in a batch mode operation,or may be operated in a continuous mode of operations. In a batch modeoperation, the necessary reactants and catalyst system are combined andallowed to react. After a period of time, the reaction mixture isremoved from the reactor and separated to recover products. Autoclavereactions are common examples of batch reactions. While the process maybe operated in the batch mode, there are advantages to operating in thecontinuous mode, especially in larger scale operations. The followingdescription will focus on continuous mode operation, although the focusof the following description does not limit the scope of the invention.

Unlike batch system operations, in a continuous process, the feedstockis continually being introduced into the reaction zone as a flowingstream and a product comprising a polyol is being continuouslywithdrawn. Materials must be capable of being transported from a lowpressure source into the reaction zone, and products must be capable ofbeing transported from the reaction zone to the product recovery zone.Depending upon the mode of operation, residual solids, if any, must becapable of being removed from the reaction zone.

A challenge in processing a feedstock comprising saccharide in apressurized hydrogen environment is that the feedstock may be aninsoluble solid. Therefore, pretreatment of the feedstock may beperformed in order to facilitate the continuous transporting of thefeedstock. Suitable pretreatment operations may include sizing, drying,grinding, hot water treatment, steam treatment, hydrolysis, pyrolysis,thermal treatment, chemical treatment, biological treatment, catalytictreatment, and combinations thereof. Sizing, grinding or drying mayresult in solid particles of a size that may be flowed or moved througha continuous process using a liquid or gas flow, or mechanical means. Anexample of a chemical treatment is mild acid hydrolysis ofpolysaccharide. Examples of catalytic treatments are catalytichydrolysis of polysaccharide, catalytic hydrogenation of polysaccharide,or both, and an example of biological treatment is enzymatic hydrolysis.Hot water treatment, steam treatment, thermal treatment, chemicaltreatment, biological treatment, or catalytic treatment may result inlower molecular weight saccharides and depolymerized lignins that aremore easily transported as compared to the untreated saccharide.Suitable pretreatment techniques are found in “Catalytic Hydrogenationof Corn Stalk to Ethylene Glycol and 1,2-Propylene Glycol” Meng Pang,Mingyuan Zheng, Aiqin Wang, and Tao Zhang Ind. Eng. Chem. Res. DOI:10.1021/ie102505y, Publication Date (Web): Apr. 20, 2011. See also, U.S.2002/0059991.

Another challenge in processing a feedstock comprising saccharide isthat the saccharide is thermally sensitive. Exposure to excessiveheating prior to contacting with the catalyst may result in undesiredthermal reactions of the saccharide such as charring of the saccharide.In one embodiment of the invention, the feedstock comprising saccharideis provided to the reaction zone containing the catalyst in a separateinput stream from the primary hydrogen stream. In this embodiment, thereaction zone has at least two input streams. The first input streamcomprises at least the feedstock comprising saccharide, and the secondinput stream comprises at least hydrogen. Water may be present in thefirst input stream, the second input stream or in both input streams.Some hydrogen may also be present in the first input stream with thefeedstock comprising saccharide. By separating the feedstock comprisingsaccharide and the hydrogen into two independent input streams, thehydrogen stream may be heated in excess of the reaction temperaturewithout also heating the feedstock comprising saccharide to reactiontemperature. The temperature of first input stream comprising at leastthe feedstock comprising saccharide may be controlled not to exceed thetemperature of unwanted thermal side reactions. For example, thetemperature of first input stream comprising at least the feedstockcomprising saccharide may be controlled not to exceed the decompositiontemperature of the saccharide or the charring temperature of thesaccharide. The first input stream, the second input stream, or both maybe pressurized to reaction pressure before being introduced to thereaction zone.

In the continuous processing embodiment, the feedstock comprisingsaccharide, after any pretreatment, is continuously introduced to acatalytic reaction zone as a flowing stream. Water and hydrogen, bothreactants, are present in the reaction zone. As discussed above anddepending upon the specific embodiment, at least a portion of thehydrogen may be introduced separately and independent from the feedstockcomprising saccharide, or any combination of reactants, includingfeedstock comprising saccharide, may be combined and introduced to thereaction zone together. Because of the mixed phases likely to be presentin the reaction zone specific types of reactor systems are preferred.For example, suitable reactor systems include ebullating catalyst bedreactor systems, immobilized catalyst reactor systems having catalystchannels, augured reactor systems, fluidized bed reactor systems,mechanically mixed reactor systems and slurry reactor systems, alsoknown as a three phase bubble column reactor systems.

Furthermore, metallurgy of the reactor system is selected to becompatible with the reactants and the desired products within the rangeof operating conditions. Examples of suitable metallurgy for the reactorsystem include titanium, zirconium, stainless steel, carbon steel havinghydrogen embrittlement resistant coating, carbon steel having corrosionresistant coating. In one embodiment, the metallurgy of the reactionsystem includes zirconium either coated or clad carbon steel.

Within the reaction zone and at operating conditions, the reactantsproceed through catalytic conversion reactions to produce at least onepolyol. Desired polyols include ethylene glycol and propylene glycol.Co-products may also be produced and include compounds such as alcohols,organic acids, aldehydes, monosaccharides, saccharides, phenoliccompounds, hydrocarbons, glycerol, depolymerized lignin, carbohydrates,and proteins. The co-products may have value and may be recovered inaddition to the product polyols. The reactions may proceed tocompletion, or some reactants and intermediates may remain in a mixturewith the products. Intermediates, which are included herein as part ofthe co-products, may include compounds such as depolymerized cellulose,lignin, and hemicellulose. Unreacted hydrogen, water, and saccharide mayalso be present in the reaction zone effluent along with products andco-products. Unreacted material and or intermediates may be recoveredand recycled to the reaction zone.

The reactions are catalytic reactions and the reaction zone comprises atleast one catalyst system. The catalyst system for conversion ofsaccharide to at least one polyol comprises an unsupported componentcomprising a compound selected from the group consisting of a tungstencompound, a molybdenum compound, and any combination thereof; and asupported component comprising an active metal component selected fromthe group consisting of Pt, Pd, Ru, Rh, Ni, Ir, and combinations thereofon a solid catalyst support. Multiple active metals may be present onthe solid catalyst support. Examples of suitable unsupported componentsinclude tungstic acid, molybedic acid, ammonium tungstate, ammoniummetatungstate, ammonium paratungstate, tungstate compounds comprising atleast one Group I or II element, metatungstate compounds comprising atleast one Group I or II element, paratungstate compounds comprising atleast one Group I or II element, heteropoly compounds of tungsten,heteropoly compounds of molybdenum, tungsten oxides, molybdenum oxides,and combinations thereof. One or more unsupported catalyst componentsmay be used with one or more supported catalyst components. The catalystsystem may also be considered a multi-component catalyst, and the termsare used herein interchangeably.

The supported catalyst component of the catalyst system requires a solidcatalyst support. The support may be in the shape of a powder, orspecific shapes such as spheres, extrudates, pills, pellets, tablets,irregularly shaped particles, monolithic structures, catalyticallycoated tubes, or catalytically coated heat exchanger surfaces. Theactive metal may be incorporated onto the catalytic support in anysuitable manner known in the art, such as by coprecipitation,coextrusion with the support, or impregnation. The active metal may bein the reduced form. Refractory oxide catalyst supports and others maybe used. Examples of the refractory inorganic oxide supports include butare not limited to silica, aluminas, silica-alumina, titania, zirconia,magnesia, clays, zeolites, molecular sieves, etc. It should be pointedout that silica-alumina is not a mixture of silica and alumina but meansan acidic and amorphous material that has been cogelled orcoprecipitated. Carbon and activated carbon may also be employed assupports. Specific suitable supports include carbon, activated carbon,Al2O3, ZrO2, SiO2, MgO, CexZrOy, TiO2, SiC, silica alumina, zeolites,clays and combinations thereof. Of course, combinations of materials canbe used as the support. The active metal may comprise from about 0.05 toabout 30 mass % of the supported catalyst component. In anotherembodiment of the invention the active metal may comprise from about 0.3to about 15 mass % of the supported catalyst component, and in anotherembodiment of the invention the active metal may comprise from about 0.5to about 7 mass % of the supported catalyst component.

The amount of the catalyst system used in the process may range fromabout 0.005 to about 0.4 mass % of the feedstock comprising saccharide,with the catalyst system measured on an elemental basis. In otherembodiment, the amount of the catalyst system used in the process mayrange from about 0.01 to about 0.25 mass % of the feedstock comprisingsaccharide with the catalyst system measured on an elemental basis. Instill other embodiment, the amount of the catalyst system used in theprocess may range from about 0.02 to about 0.15 mass % of the feedstockcomprising saccharide with the catalyst system measured on an elementalbasis. The reactions occurring are multi-step reactions and differentamounts of the catalyst system, or relative amounts of the components ofthe catalyst system, can be used to control the rates of the differentreactions. Individual applications may have differing requirements as tothe amounts of the catalyst system, or relative amounts of thecomponents of the catalyst system used. Within the catalyst system, themass ratio of unsupported component to supported component ranges fromabout 1:100 to about 100:1 as measured by ICP or other common wetchemical methods, and on an elemental basis. In another embodiment, themass ratio of unsupported component to supported component ranges fromabout 1:20 to about 50:1, on an elemental basis and the mass ratio ofunsupported component to supported component ranges from about 1:10 toabout 10:1, on an elemental basis.

In one embodiment of the invention, the unsupported catalyst componentmay be a solid that is soluble in the reaction mixture, or at leastpartially soluble in the reaction mixture which includes at least waterand the feedstock at reaction conditions. An effective amount of theunsupported catalyst should be soluble in the reaction mixture.Different applications and different unsupported catalyst componentswill result in differing effective amounts of unsupported catalystcomponent needed to be in solution in the reaction mixture. In anotherembodiment of the invention, the unsupported catalyst component is aliquid which is miscible or at least partially miscible with thereaction mixture. As with the solid unsupported catalyst component, aneffective amount of the liquid unsupported catalyst should be misciblein the reaction mixture. Again, different applications and differentunsupported catalyst components will result in differing effectiveamounts of unsupported catalyst component needed to be miscible in thereaction mixture. Typically, the amount of unsupported catalystcomponent miscible in water is in the range of about 1 to about 100%, onan elemental basis, in another embodiment, from about 10 to about 100%,on an elemental basis, and in still another embodiment, from about 20 toabout 100%, on an elemental basis.

The multicomponent catalyst of the present invention may provide severaladvantages over a more traditional single component catalyst. Forexample, the manufacture costs of the catalyst may be reduced sincefewer active components need to be incorporated onto a solid catalystsupport. Operational costs may be reduced since it is envisioned thatless catalyst make-up will be required and more selective processingsteps can be used for recovery and recycle of catalyst. Other advantagesinclude improved catalyst stability which leads to lower catalystconsumption and lower cost per unit of polyol product, and the potentialfor improved selectivity to ethylene glycol and propylene glycol withreduced production of co-boiling impurities such as butane diols.

In some embodiments the catalyst system may be contained within thereaction zone, and in other embodiments the catalyst may continuously orintermittently pass through the reaction zone, and in still otherembodiments, the catalyst system may do both, with at least one catalystsystem component residing in a reaction zone while the other catalystsystem component continuously or intermittently passes through thereaction zone. Suitable reactor systems include an ebullating catalystbed reactor system, an immobilized catalyst reactor system havingcatalyst channels, an augured reactor system, a fluidized bed reactorsystem, a mechanically mixed reactor systems and a slurry reactorsystem, also known as a three phase bubble column reactor system andcombinations thereof.

Examples of operating conditions in the rector system includetemperatures ranging from about 100° C. to about 350° C. and hydrogenpressures greater than about 150 psig. In one embodiment, thetemperature in the reactor system may range from about 150° C. to about350° C., in another embodiment the temperature in the reactor system mayrange from about 200° C. to about 280° C. The feedstock, which comprisesat least one saccharide, may be continuously contacted with the catalystsystem in the reactor system at a water to feedstock weight ratioranging from about 1 to about 100, a catalyst system (unsupportedcomponent+supported component) to feedstock weight ratio of greater thanabout 0.005, with the catalyst system measured on an elemental basis, apH of less than about 10 and a residence time of greater than 5 minutes.In another embodiment, the water to feedstock weight ratio ranges fromabout 1 to about 20 and the catalyst system to feedstock weight ratio isgreater than about 0.01, with the catalyst system measured on anelemental basis. In yet another embodiment, the water to feedstockweight ratio ranges from about 1 to about 5 and the catalyst system tofeedstock weight ratio is greater than about 0.1, with the catalystsystem measured on an elemental basis.

In one embodiment of the invention, the catalytic reaction systememploys a slurry reactor. Slurry reactors are also known as three phasebubble column reactors. Slurry reactor systems are known in the art andan example of a slurry reactor system is described in U.S. Pat. No.5,616,304 and in Topical Report, Slurry Reactor Design Studies, DOEProject No. DE-AC22-89PC89867, Reactor Cost Comparisons. The catalystsystem may be mixed with the water and feedstock comprising saccharideto form a slurry which is conducted to the slurry reactor. The reactionsoccur within the slurry reactor and the catalyst is transported with theeffluent stream out of the reactor system. The slurry reactor system maybe operated at conditions listed above. In another embodiment thecatalytic reaction system employs an ebullating bed reactor. Ebullatingbed reactor systems are known in the art and an example of an ebullatingbed reactor system is described in U.S. Pat. No. 6,436,279.

The effluent stream from the reaction zone contains at least the productpolyol(s) and may also contain unreacted water, hydrogen, saccharide,byproducts such as phenolic compounds and glycerol, and intermediatessuch as depolymerized polysaccharides and lignins. Depending upon thecatalyst selected and the catalytic reaction system used, the effluentstream may also contain at least a portion of the catalyst system. Theeffluent stream may contain a portion of the catalyst system that is inthe liquid phase, or a portion of the catalyst system that is in thesolid phase. In some embodiments it may be advantageous to remove solidphase catalyst components from the effluent stream, either before orafter and desired products or by-products are recovered. Solid phasecatalyst components may be removed from the effluent stream using one ormore techniques such as direct filtration, settling followed byfiltration, hydrocyclone, fractionation, centrifugation, the use offlocculants, precipitation, extraction, evaporation, or combinationsthereof. In one embodiment, separated catalyst may be recycled to thereaction zone.

Turning to FIG. 1, the catalyst system, water, and feedstock comprisingsaccharide are conducted via stream 122 to reaction zone 124. Themixture in stream 122 has, for example, a water to feedstock comprisingsaccharide weight ratio of about 5 and a catalyst system to feedstockcomprising saccharide weight ratio of about 0.05. At least hydrogen isconducted via stream 125 to reaction zone 124. Reaction zone 124 isoperated, for example, at a temperature of about 250° C. a hydrogenpressure of about 1200 psig, a pH of about 7 and a residence time ofabout 8 minutes. Prior to introduction into reaction zone 124, thecatalyst, water, and feedstock comprising saccharide in stream 122 andthe hydrogen in stream 125 are brought to a pressure of about 1800 psigto be at about the same pressure as reaction zone 124. However, onlystream 125 comprising at least hydrogen is raised to at least 250° C. tobe at a temperature greater than or equal to the temperature in reactionzone 124. The mixture in stream 122 which contains at least thesaccharide is temperature controlled to remain at a temperature lowerthan the decomposition or charring temperature of the saccharide. Inreaction zone 124, the saccharide is catalytically converted into atleast ethylene glycol or propylene glycol. Reaction zone effluent 126contains at least the product ethylene glycol or propylene glycol.Reaction zone effluent 126 may also contain alcohols, organic acids,aldehydes, monosaccharides, polysaccharides, phenolic compounds,hydrocarbons, glycerol, depolymerized lignin, and proteins. Reactionzone effluent 126 is conducted to product recovery zone 134 where thedesired glycol products are separated and recovered in steam 136.Remaining components of reaction zone effluent 126 are removed fromproduct recovery zone 134 in stream 138.

Turning to FIG. 2, water and feedstock comprising polysaccharide 210 isintroduced to pretreatment unit 220 where the saccharide is ground to aparticle size that is small enough to be pumped as a slurry with thewater using conventional equipment. The pretreated feedstock is combinedwith water in line 219 and catalyst system in line 223 and combinedstream 227 is conducted to reaction zone 224. The combined stream 227has, for example, a water to feedstock comprising saccharide weightratio of about 20 and a catalyst system to saccharide weight ratio ofabout 0.1. At least hydrogen is conducted via stream 225 to reactionzone 224. Some hydrogen may be combined with stream 227 prior toreaction zone 224 as shown by optional dotted line 221. Reaction zone224 is operated, for example, at a temperature of about 280° C. ahydrogen pressure of about 200 psig, a pH of about 7 and a residencetime of about 8 minutes. Prior to introduction into reaction zone 224,the catalyst system, water, and pretreated feedstock comprisingsaccharide in stream 227 and the hydrogen in stream 225 are brought to apressure of about 1800 psig to be at about the same temperature asreaction zone 224. However, only stream 225 comprising at least hydrogenis raised to at least 250° C. to be at a temperature greater than orequal to the temperature of reaction zone 224. The mixture in stream 227which contains at least the saccharide is temperature controlled toremain at a temperature lower than the decomposition or charringtemperature of the polysaccharide. In reaction zone 224, the saccharideis catalytically converted into at least ethylene glycol or polyethyleneglycol.

Reaction zone effluent 226 contains at least the product ethylene glycolor propylene glycol and catalyst. Reaction zone effluent 226 may alsocontain alcohols, organic acids, aldehydes, monosaccharides,polysaccharides, phenolic compounds, hydrocarbons, glycerol,depolymerized lignin, and proteins. Reaction zone effluent 226 isconducted to optional catalyst system recovery zone 228 where catalystcomponents are separated from reaction zone effluent 226 and removed inline 232. Catalyst components in line 232 may optionally be recycled tocombine with line 223 or to reaction zone 224 as shown by optionaldotted line 229. The catalyst component-depleted reaction zone effluent230 is conducted to product recovery zone 234 where the desired glycolproducts are separated and recovered in steam 236. Remaining componentsof effluent 230 are removed from product recovery zone 234 in stream238.

EXAMPLE

Seventeen experiments were conducted according to the followingprocedure. 1 gram of saccharide containing feedstock and 100 grams ofde-ionized water were added to a 300 ml Parr autoclave reactor. Aneffective amount of catalyst containing supported and unsupportedcomponents were added to the reactor. Details of the feedstocks and typeand amount of catalyst are shown in the Table. The autoclave was sealedand purged with N₂ followed by H₂ and finally pressurized with H₂ toabout 6 MPa at room temperature. The autoclave was heated up to 245° C.with constant stirring at about 1000 rpm and kept at temperature for 30minutes. After 30 minutes, the autoclave was cooled down to roomtemperature and liquid product was recovered by filtration and analyzedusing HPLC. Microcrystalline cellulose was obtained from Sigma-Aldrich.Ni on Norit CA-1 catalyst was prepared by impregnating various amountsof Ni using Ni nitrate in water onto activated carbon support Norit-CA1using incipient wetness technique. The impregnated support was thendried at 40° C. overnight in an oven with nitrogen purge and reduced inH2 at 750° C. for 1 hrs. 5% Pd/C and 5% Pt/C were purchased from JohnsonMatthey. Ethylene glycol and propylene glycol yields were measured asmass of ethylene glycol or propylene glycol produced divided by the massof feedstock used and multiplied by 100.

Supported Feedstock Unsupported M1 in Catalyst M2 in (M1 + M2)/ EG PGFeedstock Amount Catalyst Component Reactor Component Reactor M1/M2Feed-stock Yield Yield No. Type (g) H2O (g) (M1) (g) (M2) (g) (wt/wt)(wt/wt) (wt %) (wt %) 1 Microcrystalline 1 100 None 0 2% Ni/Norit 0.0060.0 0.006 2.3 1.9 Cellulose CA-1 2 Microcrystalline 1 100 Tungstic Acid,0.015 2% Ni/Norit 0.006 2.5 0.021 58.0 4.3 Cellulose WO3•xH2O CA-1 3Microcrystalline 1 100 Tungsten Oxide, WO₂ 0.008 0.6% 0.0018 4.4 0.01055.0 4.1 Cellulose Ni/Norit CA-1 4 Microcrystalline 1 100Phosphotungstic Acid 0.015 2% Ni/Norit 0.006 2.5 0.021 46.0 4.6Cellulose H₃PW₁₂O₄₀ CA-1 5 Microcrystalline 1 100 Ammonium 0.015 2%Ni/Norit 0.006 2.5 0.021 56.0 3.0 Cellulose Metatungstate CA-1(NH₄)₆(W₁₂O₄₀)•xH₂O 6 Microcrystalline 1 100 Ammonium 0.03 2% Ni/Norit0.006 5.0 0.036 55.0 3.0 Cellulose Metatungstate CA-1(NH₄)₆(W₁₂O₄₀)•xH₂O 7 Microcrystalline 1 100 Ammonium 0.06 2% Ni/Norit0.006 10.0 0.066 49.0 2.0 Cellulose Metatungstate CA-1(NH₄)₆(W₁₂O₄₀)•xH₂O 8 Microcrystalline 1 100 Ammonium 0.12 2% Ni/Norit0.006 20.0 0.126 37.0 1.7 Cellulose Metatungstate CA-1(NH₄)₆(W₁₂O₄₀)•xH₂O 9 Microcrystalline 1 100 Ammonium 0.015 1% Ni/Norit0.003 5.0 0.018 68.0 2.8 Cellulose Metatungstate CA-1(NH₄)₆(W₁₂O₄₀)•xH₂O 10 Microcrystalline 1 100 Ammonium 0.008 0.6% 0.00184.4 0.010 68.0 3.3 Cellulose Metatungstate Ni/Norit (NH₄)₆(W₁₂O₄₀)•xH₂OCA-1 11 Microcrystalline 1 100 Ammonium 0.008 0.2% 0.0006 13.3 0.00938.0 0.0 Cellulose Metatungstate Ni/CA-1 (NH₄)₆(W₁₂O₄₀)•xH₂O 12Microcrystalline 1 100 Ammonium 0.06 5% Pd/C 0.015 4.0 0.075 48.0 0.0Cellulose Metatungstate (NH₄)₆(W₁₂O₄₀)•xH₂O 13 Microcrystalline 1 100Ammonium 0.015 5% Pd/C 0.015 1.0 0.030 42.0 1.0 Cellulose Metatungstate(NH₄)₆(W₁₂O₄₀)•xH₂O 14 Microcrystalline 1 100 Ammonium 0.015 5% Pt/C0.015 1.0 0.030 17.2 2.4 Cellulose Metatungstate (NH₄)₆(W₁₂O₄₀)•xH₂O 15Bleached Pulp 1 100 Ammonium 0.008 0.6% 0.0018 4.4 0.010 37.0 3.0Metatungstate Ni/Norit (NH₄)₆(W₁₂O₄₀)•xH₂O CA-1 16 Glucose 1 100Ammonium 0.008 0.6% 0.0018 4.4 0.010 29.0 6.6 Metatungstate Ni/Norit(NH₄)₆(W₁₂O₄₀)•xH₂O CA-1 17 Glucose 1 100 Ammonium 0.008 0.6% 0.0018 4.40.010 49.0 4.1 Metatungstate Ni/Norit (NH₄)₆(W₁₂O₄₀)•xH₂O CA-1

1. A process for generating at least one polyol from a feedstockcomprising: a) contacting, hydrogen, water, and a feedstock comprisingat least one saccharide, with a catalyst system comprising anunsupported component comprising a compound selected from the groupconsisting of a tungsten compound, a molybdenum compound, and anycombination thereof, and a supported component comprising a supportedactive metal component selected from the group consisting of Pt, Pd, Ru,Rh, Ni, Ir, and combinations thereof on a solid catalyst support, togenerate an effluent stream comprising at least one polyol; and b)recovering the polyol from the effluent stream.
 2. The process of claim1 wherein the process is operated in a mode selected from the groupconsisting of batch mode operation and continuous mode operation.
 3. Theprocess of claim 1 wherein the contacting occurs in a reaction zonecomprising at least a first input stream and a second input stream, thefirst input stream comprising at least flowing feedstock comprisingsaccharide and the second input stream comprising flowing hydrogen. 4.The process of claim 3 wherein the first input stream is pressurizedprior to the reaction zone and the second input stream is pressurizedand heated prior to the reaction zone.
 5. The process of claim 3 whereinthe first input stream is pressurized and heated to a temperature belowthe decomposition temperature of the saccharide prior to the reactionzone and the second input stream is pressurized and heated prior to thereaction zone.
 6. The process of claim 3 wherein the first input streamand the second input stream further comprise water.
 7. The process ofclaim 1 wherein the saccharide of the feedstock is selected from thegroup consisting of monosaccharides, disaccharides, oligosaccharides,polysaccharides, and combinations thereof.
 8. The process of claim 1wherein the feedstock comprising saccharide is selected from the groupconsisting edible saccharides, inedible saccharides, waste materials,recycled materials, and combinations thereof.
 9. The process of claim 1wherein the feedstock comprising saccharide is selected from the groupconsisting of short rotation forestry, industrial wood waste, forestresidue, agricultural residue, energy crops, industrial wastewater,municipal wastewater, paper, cardboard, fabrics, pulp derived frombiomass, corn starch, sugarcane, grain, sugar beet, glycogen, moleculescomprising the molecular unit structure of C_(m)(H₂O)_(n), andcombinations thereof.
 10. The process of claim 1 wherein the polyol isselected from the group consisting of ethylene glycol and propyleneglycol.
 11. The process of claim 1 wherein the effluent stream furthercomprises at least one co-product selected from the group consisting ofalcohols, organic acids, aldehydes, monosaccharides, polysaccharides,phenolic compounds, hydrocarbons, glycerol, depolymerized lignin, andproteins.
 12. The process of claim 1 further comprising preparing thefeedstock comprising saccharide prior to contacting with the catalyst bya technique selected from the group consisting of sizing, drying,grinding, hot water treatment, steam treatment, hydrolysis, pyrolysis,thermal treatment, chemical treatment, biological treatment, catalytictreatment, and combinations thereof.
 13. The process of claim 12 whereinthe chemical treatment comprises acid catalyzed hydrolysis or basecatalyzed hydrolysis, wherein the catalytic treatment comprisesdepolymerization, catalytic hydrogenation, or both, and wherein thebiological treatment comprises enzymatic hydrolysis.
 14. The process ofclaim 1 wherein the hydrogen, water, and feedstock is contacted with thecatalyst in a reactor having metallurgy comprising a component selectedfrom the group consisting of titanium, zirconium, stainless steel,carbon steel having hydrogen embrittlement resistant coating, carbonsteel having corrosion resistant coating.
 15. The process of claim 1wherein the hydrogen, water, and feedstock is contacted with thecatalyst in a system selected from the group consisting of an ebullatingcatalyst bed system, an immobilized catalyst system having catalystchannels, an augured reaction system, a fluidized bed reaction system, amechanically mixed reaction system, and a slurry reactor system.
 16. Theprocess of claim 1 wherein the flowing hydrogen, water, and feedstockare contacted with the catalyst system in a reactor system operated at atemperature ranging from about 100° C. to about 350° C. and a hydrogenpressure greater than about 150 psig.
 17. The process of claim 1 whereinthe hydrogen, water, and feedstock are contacted with the catalyst in areaction zone operated at conditions sufficient to maintain at least aportion of the water in the liquid phase.
 18. The process of claim 1wherein the hydrogen, water, and feedstock are continuously contactedwith the catalyst system in a reactor system operated at a water tosaccharide weight ratio ranging from about 1 to about 100, a catalyst tosaccharide weight ratio of greater than about 0.005, the catalystmeasured on an elemental basis, a pH of less than about 10 and aresidence time of greater than 5 minutes.
 19. The process of claim 1wherein the effluent stream further comprises catalyst, said processfurther comprising separating at least one catalyst component from theeffluent stream using a technique selected from the group consisting ofdirect filtration, settling followed by filtration, hydrocyclone,fractionation, centrifugation, the use of flocculants, precipitation,liquid extraction, evaporation, and combinations thereof.
 20. Theprocess of claim 19 said process further comprising recycling theseparated catalyst component to the reactor.